Global three-parameter model for neutrino oscillations using Lorentz violation

A model of neutrino oscillations is presented that has only three degrees of freedom and is consistent with existing data. The model is a subset of the renormalizable sector of the Standard-Model Extension (SME), and it offers an alternative to the standard three-neutrino massive model. All classes of neutrino data are described, including solar, reactor, atmospheric, and LSND oscillations. The disappearance of solar neutrinos is obtained without matter-enhanced oscillations. Quantitative predictions are offered for the ongoing MiniBooNE experiment and for the future experiments OscSNS, NOvA, and T2K.Comment: 12 pages REVTe

Noncommutative Field Theory and Lorentz Violation

The role of Lorentz symmetry in noncommutative field theory is considered. Any realistic noncommutative theory is found to be physically equivalent to a subset of a general Lorentz-violating standard-model extension involving ordinary fields. Some theoretical consequences are discussed. Existing experiments bound the scale of the noncommutativity parameter to (10 TeV)^{-2}.Comment: 4 page

Supersymmetry and Lorentz Violation

Supersymmetric field theories can be constructed that violate Lorentz and CPT symmetry. We illustrate this with some simple examples related to the original Wess-Zumino model.Comment: 4 page

Spacetime-varying couplings and Lorentz violation

Spacetime-varying coupling constants can be associated with violations of local Lorentz invariance and CPT symmetry. An analytical supergravity cosmology with time-varying fine-structure constant provides an explicit example. Estimates are made for some experimental constraints.Comment: 4 page

Spontaneous Lorentz Violation, Nambu-Goldstone Modes, and Gravity

The fate of the Nambu-Goldstone modes arising from spontaneous Lorentz violation is investigated. Using the vierbein formalism, it is shown that up to 10 Lorentz and diffeomorphism Nambu-Goldstone modes can appear and that they are contained within the 10 modes of the vierbein associated with gauge degrees of freedom in a Lorentz-invariant theory. A general treatment of spontaneous local Lorentz and diffeomorphism violation is given for various spacetimes, and the fate of the Nambu-Goldstone modes is shown to depend on both the spacetime geometry and the dynamics of the tensor field triggering the spontaneous Lorentz violation. The results are illustrated within the general class of bumblebee models involving vacuum values for a vector field. In Minkowski and Riemann spacetimes, the bumblebee model provides a dynamical theory generating a photon as a Nambu-Goldstone boson for spontaneous Lorentz violation. The Maxwell and Einstein-Maxwell actions are automatically recovered in axial gauge. Associated effects of potential experimental relevance include Lorentz-violating couplings in the matter and gravitational sectors of the Standard-Model Extension and unconventional Lorentz-invariant couplings. In Riemann-Cartan spacetime, the possibility also exists of a Higgs mechanism for the spin connection, leading to the absorption of the propagating Nambu-Goldstone modes into the torsion component of the gravitational field.Comment: 16 pages REVTe

The Arizona CDFS Environment Survey (ACES): A Magellan/IMACS Spectroscopic Survey of the Chandra Deep Field South

We present the Arizona CDFS Environment Survey (ACES), a recently-completed spectroscopic redshift survey of the Chandra Deep Field South (CDFS) conducted using IMACS on the Magellan-Baade telescope. In total, the survey targeted 7277 unique sources down to a limiting magnitude of R = 24.1, yielding 5080 secure redshifts across the ~30' x 30' extended CDFS region. The ACES dataset delivers a significant increase to both the spatial coverage and the sampling density of the spectroscopic observations in the field. Combined with previously-published, spectroscopic redshifts, ACES now creates a highly-complete survey of the galaxy population at R < 23, enabling the local galaxy density (or environment) on relatively small scales (~1 Mpc) to be measured at z < 1 in one of the most heavily-studied and data-rich fields in the sky. Here, we describe the motivation, design, and implementation of the survey and present a preliminary redshift and environment catalog. In addition, we utilize the ACES spectroscopic redshift catalog to assess the quality of photometric redshifts from both the COMBO-17 and MUSYC imaging surveys of the CDFS.Comment: resubmitted to MNRAS; 12 pages, 12 figures, and 3 tables; updated redshift catalog available at http://mur.ps.uci.edu/~cooper/ACES

Weak charge form factor and radius of 208Pb through parity violation in electron scattering

We use distorted wave electron scattering calculations to extract the weak charge form factor F_W(q), the weak charge radius R_W, and the point neutron radius R_n, of 208Pb from the PREX parity violating asymmetry measurement. The form factor is the Fourier transform of the weak charge density at the average momentum transfer q=0.475 fm$^{-1}$. We find F_W(q) =0.204 \pm 0.028 (exp) \pm 0.001 (model). We use the Helm model to infer the weak radius from F_W(q). We find R_W= 5.826 \pm 0.181 (exp) \pm 0.027 (model) fm. Here the exp error includes PREX statistical and systematic errors, while the model error describes the uncertainty in R_W from uncertainties in the surface thickness \sigma of the weak charge density. The weak radius is larger than the charge radius, implying a "weak charge skin" where the surface region is relatively enriched in weak charges compared to (electromagnetic) charges. We extract the point neutron radius R_n=5.751 \pm 0.175 (exp) \pm 0.026 (model) \pm 0.005 (strange) fm$, from R_W. Here there is only a very small error (strange) from possible strange quark contributions. We find R_n to be slightly smaller than R_W because of the nucleon's size. Finally, we find a neutron skin thickness of R_n-R_p=0.302\pm 0.175 (exp) \pm 0.026 (model) \pm 0.005 (strange) fm, where R_p is the point proton radius.Comment: 5 pages, 1 figure, published in Phys Rev. C. Only one change in this version: we have added one author, also to metadat

Minimum-Uncertainty Angular Wave Packets and Quantized Mean Values

Uncertainty relations between a bounded coordinate operator and a conjugate momentum operator frequently appear in quantum mechanics. We prove that physically reasonable minimum-uncertainty solutions to such relations have quantized expectation values of the conjugate momentum. This implies, for example, that the mean angular momentum is quantized for any minimum-uncertainty state obtained from any uncertainty relation involving the angular-momentum operator and a conjugate coordinate. Experiments specifically seeking to create minimum-uncertainty states localized in angular coordinates therefore must produce packets with integer angular momentum.Comment: accepted for publication in Physical Review

Search for Neutrinoless Double-Beta Decay in 136^{136}Xe with EXO-200

We report on a search for neutrinoless double-beta decay of $^{136}$Xe with EXO-200. No signal is observed for an exposure of 32.5 kg-yr, with a background of ~1.5 x 10^{-3} /(kg yr keV) in the $\pm 1\sigma$ region of interest. This sets a lower limit on the half-life of the neutrinoless double-beta decay $T_{1/2}^{0\nu\beta\beta}$($^{136}$Xe) > 1.6 x 10$^{25}$ yr (90% CL), corresponding to effective Majorana masses of less than 140-380 meV, depending on the matrix element calculation